1. Field of the Invention
The present invention relates to a thin film magnetic recording head used for, for example, a floating magnetic head. More particularly, the present invention relates to a thin film magnetic head intended to decrease inductance to be made adaptable to higher recording frequencies, and a method of manufacturing the same.
2. Description of the Related Art
FIG. 18 is a partial front view showing the structure of a conventional thin film magnetic head (inductive head). FIG. 19 is a partial sectional view of the thin film magnetic head shown in FIG. 18 taken along line XIXxe2x80x94XIX, as viewed from the direction of arrows.
In FIGS. 18 and 19, the bottom core layer 1 is made of a magnetic material such as permalloy or the like. An insulating layer 9 is formed on the bottom core layer 1. The insulating layer 9 has a trench 9a which is formed in the height direction (the Y direction shown in FIG. 18) from the air bearing surface (referred to as xe2x80x9cABSxe2x80x9d hereinafter) facing a recording medium to have an inner width dimension equal to the track width Tw.
Also, a bottom pole layer 3 magnetically connected to the bottom core layer 1, a gap layer 4 and a top pole layer 5 magnetically connected to a top core layer 6 are formed in the trench 9a by plating in turn from the bottom.
As shown in FIG. 19, a coil layer 7 patterned in a spiral shape is provided on the portion of the insulating layer 9, which is located at the back of the trench 9a formed in the insulating layer 9 in the height direction (the Y direction shown in FIG. 19).
The coil layer 7 is covered with an organic insulating layer 8 of resist or the like. The top core layer 6 is formed on the organic insulating layer 8. The front end 6a of the top core layer 6 is magnetically connected to the top pole layer 5. The base end 6b is magnetically connected to the bottom core layer 1.
In the inductive head shown in FIGS. 18 and 19, when a recording current is supplied to the coil layer 7, a recording magnetic field is induced in each of the top and bottom core layers 1 and 6. A magnetic signal is recorded on a recording medium such as a hard disk by a leakage magnetic field between the bottom pole layer 3 and the top pole layer 5 magnetically connected to the bottom core layer 1 and the top core layer 6, respectively.
In the inductive head shown in FIGS. 18 and 19, the bottom pole layer 3, the gap layer 4 and the top pole layer 5 are locally formed with the track width Tw near the ABS (the surface facing the recording medium). This type of inductive head is adaptable to narrower tracks.
The method of manufacturing the inductive head shown in FIGS. 18 and 19 is described below. First, the insulating layer 9 is formed on the bottom core layer 1. The trench 9a having the track width Tw is formed in the insulating layer 9 with a predetermined length from the ABS in the height direction.
Next, the bottom pole layer 3, the gap layer 4 and the top pole layer 5 are continuously formed by plating in the trench 9a. The coil layer 7 is patterned on the portion of the insulating layer 9, which is located at the back of the trench 9a formed in the insulating layer 9.
Furthermore, the coil layer 7 is covered with the organic insulating layer 8. The top core layer 6 is formed by frame plating to extend from the top pole layer 5 to the organic insulating layer 8 to complete the inductive head shown in FIGS. 18 and 19.
It is necessary to decrease the inductance of the inductive head with track narrowing accompanying increases in recording density and recording frequency in future. In order to decrease the inductance, the magnetic path formed from the bottom core layer 1 to the top core layer 6 must be shortened. Thus, the width dimension T1 of the coil layer 7 formed between the front end 6a and the base end 6b of the top core layer 6 must be decreased. By decreasing the width dimension T1 of the coil layer 7, the length of the top core layer 6 can be shortened to realize a short magnetic path.
A possible method of decreasing the width dimension T1 of the coil layer 7 without changing the number of the turns of the coil layer 7 is one in which the coil layer 7 is formed in a laminated structure comprising two layers.
However, in the structure of the thin film magnetic head shown in FIGS. 18 and 19, even when the coil layer 7 has a simple two-layer laminated structure, the magnetic path cannot be shortened so that it is made adaptable to higher recording frequency in future, thereby causing difficulties in appropriately decreasing inductance.
This is because the coil layer 7 is formed on the thick insulating layer 9. As shown in FIG. 18, the insulating layer 9 has a thickness H5 which is more than the total thickness H6 of the bottom pole layer 3, the gap layer 4 and the top pole layer 5. Therefore, assuming that the surface of the top pole layer 5 is a reference plane, the coil layer 7 is formed on the insulating layer 9 nearer the top core layer 6 than the reference plane, as shown in FIG. 19.
Therefore, with the coil layer 7 having a two-layer laminated structure, the width dimension T1 of the coil layer 7 can be decreased, but the height from the top of the bottom core layer 1 to the top of the insulating layer 8 formed to cover the coil layer 7 is substantially increased. As a result, the magnetic path cannot be much shortened, and the inductance cannot be appropriately decreased.
In the inductive head having the structure shown in FIG. 19, with the coil layer 7 having two-layer laminated structure, the thickness dimension H1 of the organic insulating layer 8 formed to cover the coil layer 7 is increased. Thus, the organic insulating layer 8 significantly rises from the surface of the top pole layer 5 as the reference plane.
Therefore, the top core layer 6 cannot be easily formed by frame plating to extend from the top pole layer 5 to the organic insulating layer 8, thereby causing the problem of making it impossible to form the top core layer 6, particularly the portion near the front end 6a thereof, in a predetermined shape.
The present invention has been achieved for solving the above problems. An object of the invention is to provide a thin film magnetic head in which the magnetic path can be shortened to decrease inductance, and a method of manufacturing the thin film magnetic head.
A thin film magnetic head of the present invention comprises a bottom core layer, a top core layer, and a track width control portion located between the bottom and top core layers on the surface facing a recording medium and having a controlled dimension in the direction of the track width. The track width control portion comprises a gap layer magnetically insulating at least one of the bottom and top pole layers connected to the bottom and top core layers, respectively, from each of the pole layers, or one of the core layers from the corresponding one of the pole layers. When the junction surface between the track width control portion and the top core layer is the reference plane, a coil layer for inducing a recording magnetic field in the bottom and top core layers is located at the back of the track width control portion in the height direction. The upper surface of the coil layer is located nearer the bottom core layer than the reference plane. Furthermore, an insulating layer is provided between the reference plane and the bottom core layer. The coil layer is buried in the insulating layer. The top core layer is formed to extend from the track width control portion to the insulating layer so that the base end of the top core layer is magnetically connected to the bottom core layer.
In the present invention, in order to manufacture the thin the thin film magnetic head adaptable to future increases in recording density and recording frequency, particularly, the formation position of the coil layer is differentiated from that of a conventional head to realize a short magnetic path and decrease conductance.
As described above, the coil layer is located at the back of the track width control portion formed between the bottom and top core layers in the height direction. The junction surface between the track width control portion and the top core layer is the reference plane. The coil layer is located nearer the bottom core layer than the reference plane. The coil layer is buried in the insulating layer provided between the bottom core layer and the reference plane.
In the present invention, the coil layer is formed to be buried in the insulating layer formed at the back of the track width control portion. This is different from the structure of the inductive head shown in FIGS. 18 and 19 in which the coil layer 7 is formed on the insulating layer 9.
Since the coil layer is formed to be buried in the insulating layer formed at the back of the track width control portion, the height dimension from the top of the bottom core layer to the top of the insulating layer formed to cover the coil layer can be decreased to decrease the length of the top core layer, as compared with a conventional magnetic head. Therefore, it is possible to realize a short magnetic path, and appropriately decrease inductance.
In the present invention, the insulating layer preferably comprises an inorganic insulating layer, or comprises an organic insulating layer located in the pitch intervals of a conductor, which constitutes the coil layer, and an inorganic insulating layer which fills the other portions.
In the present invention, the insulating layer formed to cover the coil layer and the reference plane preferably lie in the same plane.
In this case, a second coil layer is preferably formed on the insulating layer directly or with another layer provided therebetween so as to be electrically connected to the coil layer. The top core layer is preferably formed on an insulating layer formed to cover the second coil layer.
As described above, with the coil layer having a two-layer laminated structure, the width of the coil layer can be decreased. Also, in the present invention, the first coil layer is formed within the insulating layer formed at the back of the track width control portion, and thus the height from the top of the bottom core layer to the top of the insulating layer formed to cover the second coil layer can be decreased, as compared with a conventional inductive head comprising a coil layer having a two-layer laminated structure. Therefore, the magnetic path formed from the bottom core layer to the top core layer can be shortened to decrease inductance.
Particularly, in the present invention, the first coil layer is formed to be buried in the insulating layer formed at the back of the track width control portion. The surface of the insulating layer is planarized in the same plane as the surface of the track width control portion.
Therefore, the second coil layer can be precisely patterned on the insulating layer directly or with another layer provided therebetween.
Furthermore, in the present invention, the first coil layer is formed within the insulating layer formed at the back of the track width control portion. The second coil layer is formed on the planarized surface of the insulating layer. Therefore, assuming that the surface of the track width control portion is the reference plane, the rise of the insulating layers formed to cover the coil layers corresponds to the rise of the insulating layer formed to cover the second coil layer, thereby permitting the formation of the top core layer extending from the track width control portion to the insulating layer on the second coil layer with high pattern precision.
In the present invention, the gap layer is preferably made of a nonmagnetic metallic material which can be plated. As the nonmagnetic metallic material, at least one material is preferably selected from NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
A method of manufacturing a thin film magnetic head of the present invention comprises the following steps:
(a) The step of forming a track width control portion on a bottom core layer with a predetermined width dimension and a predetermined length from the surface facing a recording medium in the height direction, the track width control portion comprising a bottom pole layer, a nonmagnetic gap layer, and a top pole layer, the bottom pole layer and the nonmagnetic gap layer, or the nonmagnetic gap layer and the top pole layer;
(b) The step of forming an insulating base layer on the portion of the bottom core layer, which is located at the back of any of the track width control portions in the height direction, and forming a coil layer on the insulating base layer so that the top of the coil layer is nearer the bottom core layer than the top of the track width control portion;
(c) The step of forming an insulating layer to cover the track width control portion and the coil layer;
(d) The step of planarizing the top surface of the insulating layer so that the planarized top surface and the top surface of the track width control portion lie in the same plane; and
(e) The step of forming the top core layer to extend from the track width control portion to the insulating layer.
In the present invention, the track width control portion comprising the pole layer and the gap layer is first formed on the bottom core layer with the predetermined length from the surface facing the recording medium in the height direction. Therefore, the insulating layer 9 shown in FIGS. 18 and 19 is not formed at the back of the track width control portion, and thus the coil layer can be formed on the portion of the bottom core layer, which is located at the back of the track width control portion, with the insulating base layer provided therebetween.
In the present invention, the insulating layer made of alumina is then formed to extend from the track width control portion to the coil layer, and the surface of the insulating layer is ground to the same plane as the surface of the track width control portion to planarize the surface of the insulating layer in the same plane as the surface of the track width control portion.
At this time, the coil layer is buried in the insulating layer.
In contrast, in the thin film magnetic head shown in FIGS. 18 and 19, the coil layer 7 cannot be formed within the insulating layer 9 during the manufacturing process.
Namely, in the method of manufacturing the thin film magnetic head shown in FIGS. 18 and 19, the insulating layer 9 is first formed on the bottom core layer 1, and thus the coil layer 7 is inevitably formed on the insulating layer 9.
As described above, the manufacturing method of the present invention can form the coil layer at the back of the track width control portion in the height direction, which is formed between the bottom core layer and the top core layer, so that assuming that the junction surface between the track width control portion and the top core layer is the reference plane, the coil layer is located nearer the bottom core layer than the reference plane.
In the present invention, the step (c) preferably comprises forming an inorganic insulating layer as the insulating layer, and the step (d) preferably comprises polishing the insulating layer so that the tops of the track width control portion and the inorganic insulating layer lie in the same plane.
Alternatively, in the present invention, the step (c) preferably comprises filling the pitch intervals of the conductor of the coil layer with an organic insulating layer, and then forming an inorganic insulating layer on the organic insulating layer and the coil layer, and the step (d) preferably comprises polishing the insulating layer so that the top surfaces of the track width control portion and the inorganic insulating layer lie in the same plane.
The present invention preferably further comprises the following step (f) after the above step (d).
(f) The step of forming a second coil layer on the planarized surface of the insulating layer directly or with another layer provided therebetween so that the second coil layer is electrically connected to the first coil layer.
In the present invention, the step (a) preferably comprises forming the gap layer by plating together with the pole layers. In this case, as the nonmagnetic metallic material which forms the gap layer and which can be plated, at least one material is preferably selected from NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.